Certain types of 4H-2,3-dihydro-1,3-oxazin-4-one derivatives are described in, for example, Tetrahedron Lett., (33), 2905 (1976), Heterocycles, 17, 298 (1982), Chem. Pharm. Bull., 35(5), 1871 (1987), etc. and thus they are known.
However, the compounds described in the abovementioned publications differ from the compounds of this invention since none of them has a tertiary alkyl substituent on the 3-position of a 1,3-oxazine ring and no mention is made of their herbicidal activity and plant growth control activity.
U.S. Pat. Nos. 5,006,157 and 5,076,834 disclose 1-(1-methyl-1-phenylethyl)-3-phenyl-1,2,5,6-tetrahydropyridin-2-one derivatives and their use as a herbicide.